brainstem overview medulla pons midbrain january 12, 2009

Brainstem

Overview

Medulla

Pons

Midbrain

January 12, 2009

Ventral – Lateral View

Midbrain

Cerebral peduncles

Pons

Basis pontis

Medulla

Pyramid Olive

Corticospinal tract descends throughout movement

Reticular formation descends throughout movement

ascends throughout arousal

Ventral – Dorsal Organization

(anterior - posterior)

Basis

Large anterior fiber tracts: cerebral peduncles, crossing pontine fibers, pyramids


Tegmentum

Anterior cell body-rich areas, floor of brainstem: red nuclei, substantia nigra, reticular formation


Tectum

Roof of the brainstem: superior colliculi, inferior colliculi: corpus quadrigemina

Cerebellum

Cuneatus, gracilis (medulla)


Basis Tegmentum

Tectum

Vertical Columns of Cranial Nerves

Internal Columns of Nuclei

III, IV, VI, XII

V, VII, N. ambiguus, XII

EW, Salivatory, DMN X

V, VII, IX, X

N. Solitary tract

VIII

Subdivisions of Vertical Columns

• Motor nuclei– Somatic motor

• closest to midline• eyes, tongue• CN III, IV, VI, XII

– Branchial motor• Lateral position• Branchial arches: chewing,

expression, middle ear, pharynx, larynx, sternomastoic, trapezius

• CN V, VII, XI• N. ambiguus (IX, X)

– Visceral motor• ventral / ventrolateral• Parasympathetic: glands, smooth

muscle, heart, lungs, GI above splenic flexure

• Edinger-Westfall (III)• Sup. & Inf. salivatory (VII)• Dorsal motor nucleus of X

• Sensory nuclei– General sensory

• lateral to branchial motor• Face, sinuses, meninges• All modalities• CN V mainly• Also CN VII, IX, X

– Visceral sensory• lateral to visceral motor• Taste; cardiorespiratory, GI info• N. of the solitary tract (CN VII, IX,

X)– Special sensory

• furthest lateral• Balance; hearing• CN VIII (vestibular)• CN VIII (cochlear)

Brainstem

Overview

Medulla

Pons

Midbrain

.

Internal Structure of Medulla

Cross section at three levels

• Level of pyramidal decussation

• Level of lemniscal decussation

• Level of inferior olivary nuclei

Level of Pyramidal Decussation

Pyramidal tract

Lateral corticospinal tract

75 – 90%

Anterior corticospinal tract -- fibers to innervate muscles of trunk

Spinal nucleus of V

From pons to C4

Gracile nucleus

Contralateral movement

Level of Lemniscal Decussation

Medial lemniscusCarries 2nd order sensory neurons to VPL thalamus

Gracile nucleus

Cuneate nucleus

Internal arcuate fibers

MLF

Pyramids

Position & vibration sense

Level of Inferior Olives

Inferior cerebellar peduncle = Restiform body

Inferior olivary nucleiRelay between cortex, vestibular nuclei, cerebellum, basal ganglia, and dorsal column nuclei

MLF

Vestibular nuclei

Medial InferiorHypoglossal nucleus CN XII

Arcuate nuclei pontine nuclei

Cranial Nerves of the Medulla

Vestibular nuclei

CN XII

Cranial Nuclei of the Medulla

N. solitarious

Sensory nucleus for CN VII, IX, X


N. solitarious


Spinal trigeminal tract

CN V, VII, IX, X


N. ambiguus

Motor nucleus for CN IX, X & XI

N. solitarious



CN V, VII, IX, X


N. ambiguus


N. solitarious



CN V, VII, IX, X

Dorsal motor nucleus of X

CN IX: Glossopharyngeal Nerve

N. ambiguus


N. solitarious



CN V, VII, IX, X


N. ambiguus


N. solitarious


Posterior 1/3 of the tongue


CN V, VII, IX, X


N. ambiguus


N. solitarious




CN V, VII, IX, X

Sensation behind ear


N. ambiguus


Stylopharyngeus (lifts pharynx)

N. solitarious




CN V, VII, IX, X



N. ambiguus


Stylopharyngeus (lifts pharynx)

N. solitarious



Inf. salivatory nucleus

Parotid gland, parasympathetic


CN V, VII, IX, X


CN X: Vagus Nerve

N. ambiguus


N. solitarious



CN V, VII, IX, X

“Wanderer”

CN X: Vagus Nerve

N. ambiguus


N. solitarious


Taste, epiglottis Cardiorespiratory


CN V, VII, IX, X

“Wanderer”

CN X: Vagus Nerve

N. ambiguus


N. solitarious




CN V, VII, IX, X

Ear

“Wanderer”

CN X: Vagus Nerve

N. ambiguus


Pharynx Larynx

N. solitarious




CN V, VII, IX, X

Ear

“Wanderer”

CN X: Vagus Nerve

N. ambiguus


Pharynx Larynx

N. solitarious





CN V, VII, IX, X

Ear

“Wanderer”

CN X: Vagus Nerve

N. ambiguus


Pharynx Larynx

N. solitarious




Parasympathetic, preganglionic


CN V, VII, IX, X

Ear

“Wanderer”

Brainstem

Overview

Medulla

Pons

Midbrain

Pons

Landmarks

Basis pontis 4th ventricle

Cerebellum and Middle cerebellar peduncle

Cranial Nerves

V, VI, VII, VIII

Pontine Nuclei

Pontine nuclei

Project to cerebellum

Continuation of arcuate nuclei (over pyramids)

Input (ipsilateral)

Motor cortex

Sensory cortex

Association cortex

Cingulate cortex

Output (contralateral)

Transverse crossing via middle cerebellar

peduncle to cerebellum

Internal Structure of the Pons


• Level of facial nucleus (CN VII)

• Level of middle cerebellar peduncle

• Level of locus ceruleus

Pons

Descending upper motor neurons

Connection of pons to cerebellum

Restiform body (inf. cerebellar peduncle)

Middle cerebellar peduncle

Medial lemniscus Ascending 2nd order

sensory neurons

4th Ventricle

Cranial Nerves of Lower Pons

CN VIII – Vestibular Nuclei Pure sensory lateral location

Balance

Posterior view: Cerebullum cut away


CN VIII –

Vestibular Nuclei

(Cochlear Nuclei)


CN VII nucleus – Facial nerve

Muscles of face

At a slightly higher level

CN VI nucleus – Abducens nerve

Abduction of eye

Longest, most vulnerable CN


CN VII nucleus - Facial nerve

Muscles of face


CN VI nucleus – Abducens nerve

Abduction of eye






Anterior view

Mid Pons4th Ventricle


Corticospinal tract, corticobulbar tract,

corticopontine fibersDescending fibers

Mid Pons4th Ventricle


Pontine nuclei in basis

Mid Pons

Pontine nuclei

Trapezoid body – transverse fibers in pontine tegmentum

from cochlear nucleus

hearing

Lateral lemniscus

Mid Pons

Pontine nuclei

Lateral lemniscus

Medial lemniscus fibers from dorsal column

(position and vibration)

Trigeminal tract pain, temperature, touch from

contralateral face

Lemniscal sensory system – in tegmentum of the pons

Cranial Nerve of the Mid Pons

4th Ventricle

CN V

Motor trigeminal nucleus


4th Ventricle

CN V


Principal trigeminal sensory nucleus


4th Ventricle

CN V


Principal trigeminal sensory nucleus

Trigeminal fascicles

Trigeminal nerve

Upper Pons4th ventricle cerebral aqueduct

Superior cerebellar peduncle decussation


Superior cerebellar peduncle

Descending upper motor neurons

Transverse ponto-cerebellar

fibers


MLF

Periaqueductal gray matter


MLFLocus ceruleus

Primary source of noradrenergic

innervation to the brain

Neurons contain melanin


MLFParabrachial Nucleus

Also release catecholamines

Neurons also contain melanin


MLFPediculopontine Nucleus

Some neurons release

acetylcholine

Other neurons release glutamate

They assist in learning and

voluntary motor control, e.g. locomotion,

saccadic eye

Brainstem

Overview

Medulla

Pons

Midbrain

MidbrainLandmarks

Cerebral peduncles Optic chiasm

Interpeduncular fossa (Superior colliculi) (Inferior colliculi)

(Superior cerebellar peduncle)

Cranial Nerves

III, IV

Patterning of the Midbrain

External Structure of Midbrain

1. Optic chiasm

2. Interpeduncular fossa

3. Oculomotor nerve (CN III)

4. Trochlear nerve (CN IV)

5. Pons

6. Cerebral peduncles (crus cerebri)

Ventral surface

(anterior)

External Structure of Midbrain

Quadrigeminal Plate

• Superior colliculus

• Inferior colliculus

Dorsal surface

Cerebellum removed

CN IV

Trochlear nerve

Cranial Nerves of the Midbrain

Anterior exit

CN III (1)

CN VI (5)

Posterior exit

CN IV (2)

MLF - Medial longitudinal fasciculus (7)

Vestibular nuclei (6)

Pons (3)

Internal Structure of Midbrain

Cross section at two levels

• Level of inferior colliculus

• Level of superior colliculus

Lower MidbrainInferior colliculus

hearing

cerebral aqueduct

DORSAL

VENTRAL

cerebral peduncles


Substantia nigra

Melanin-containing cells that produce dopamine Project to the basal ganglia


Substantia nigra

Crus cerebri

(cerebral peduncle)

Basis peduncularis


CN IV Trochlear nerve


CN IV Trochlear nerve

MLF


CN IV

MLF

Dorsal raphe nucleus – projects serotonergic fibers to basal ganglia and throughout cortex


hearing Mesencephalic

nucleus of V

analogous to dorsal root

ganglion but within

CNS

Internal Structure of Midbrain

Cross section at two levels

• Level of inferior colliculus

• Level of superior colliculus

Upper Midbrain

Superior colliculus

vision

Substantia nigra Crus cerebri (cerebral

peduncle)

Upper Midbrain

Superior colliculus

vision

Medial geniculate bodyhearing

Upper Midbrain

Vision

Superior colliculus Lateral geniculate body

Hearing

Inferior colliculus Medial geniculate body

Upper Midbrain

Superior colliculus

vision

Red nucleus – relay from cortex and cerebellum to spinal cord, inferior olive, reticular formation, cerebellum

Controls arm movement

Cranial Nerves of Upper Midbrain

Superior colliculus

vision

Red nucleusCN III Oculomotor

nucleus

Edinger Westfal nucleus

Parasympathetic to ciliary ganglion

Pupillary sphincter ciliary muscles

Cranial Nerves of Upper Midbrain

Superior colliculus

vision

Red nucleus

Edinger Westfal nucleus

MLF

CN III Oculomotor nucleus

Innervation of Eye Muscles

Dorsal view

Cerebellum removed

Innervation of Eyes & Muscles

Lacrimal gland (CN VII)

Superior rectus Inferior rectus Medial rectus Inferior Oblique

(CN III)

Superior oblique (CN IV)

Lateral rectus (CN VI)

Parasympathetic: Edinger-Westfal (CN III) Sympathetic: Superior Cervical Ganglion

Tuesday

Diencephalon

Thalamus

Hypothalamus

brainstem overview medulla pons midbrain january 12, 2009

Documents

solitarioussensory nucleus

xcranial nuclei

solitary tract cn

ambiguus motor nucleus

red nuclei

inferior colliculi

anterior corticospinal

trapeziuscn v